1. Technical Field
The present invention relates to a display controller, electronic equipment and a method for supplying image data.
2. Related Art
Mobile devices (electronic equipment in a broad sense) such as a mobile phone often have display panels including a liquid crystal display (LCD) panel in recent years. A display panel is driven by a display driver based on image data. The image data is sometimes taken by a camera module and sometimes is generated or converted by a host. The display driver receives such image data and a display synchronizing signal and performs a driving control of the display panel.
A display controller can take over the supply of the image data and the display synchronizing signal from the host. This means that the display controller can reduce a processing load of the host. Some display controllers have memories which serve as video memories with the aim of reducing power consumption.
The display controllers mounted in the mobile devices are strongly required to be driven with low power consumption. For this reason, the memory installed in the display controller was often a static random access memory (SRAM) which uses less power compared to a dynamic random access memory (DRAM). Thereby, a capacity of the memory in the display controller tended to be relatively small. However, the small capacity of the memory was enough since a display size of the LCD panel was small. Besides, a chip size of the display controller could be small. Therefore, it was an advantage in terms of cost and packaging.
Recently, there has been great demand for a LCD panel having a display size of quarter video graphics array (QVGA) (240 pixels×320 pixels) or a larger display size. When the display size becomes larger, a data size of the image data also becomes larger. Therefore, it takes a longer time to transfer the image data from the host to the memory housed in the display controller and from the display controller to the display driver. It could also happen that a perceptible flicker appears in an image which is renewed at a certain frequency in the LCD panel. In addition, a control for image data readout from the video memory becomes complicated. This tendency gets prominent when a static image data is consecutively rewritten or a motion image data is rewritten.
Furthermore, the host cannot process other transaction during this data transfer process. It leads to a low performance of the whole system.
A disadvantage in the packaging is pointed out when the capacity of the memory becomes larger and the chip size also gets larger. However, a packaging technique has advanced recently and it is not necessarily the case that the display controller embedded with the SRAM as a memory has an advantage in the packaging.
The present invention has been developed in consideration of the above-mentioned problems, and intended to provide a display controller which can prevent the system performance from being lowered and a quality of the image from being deteriorated. The present invention also intended to provide electronic equipment and a method of supplying image data.